Depression is a cause of excess disability, morbidity and mortality in older persons and often remains unrecognized. Standard methods for diagnosing depression may miss significant pathology in "normal" elderly; their validity in the presence of dementia has not even been tested. A proposed program will screen a community-based sample of older persons for overt major depressive disorder and masked depressive disorders. Similar methodology will be used to identify secondary and/or coexisting psychiatric symptoms and to diagnose affective disorders in individuals with dementing illness. In those with putative syndromes, diagnoses will be derived from medical, psychiatric and psychological workups. The syndromes will be characterized in terms of symptom clusters, individual and family psychiatric histories, functional impairment, and biological markers. Their similarity to depression as present in the general population will be determined by determining the similarity of response to treatment of a controlled trail with a standard tricyclic antidepressant drug. The treatment study will also examine the impact of treatment on both cognitive and functional abilities.